1. Field of the Invention
The present invention relates to a stage apparatus, an exposure apparatus, and a device manufacturing method.
2. Description of the Related Art
There is a problem particularly in the field of equipments, like a stage apparatus for positioning an object. For a stage, it is necessary to achieve high positioning accuracy. However, reaction-forces generated upon driving a stage cause vibration and deformation of the stage, thereby affecting the positioning accuracy. In order to reduce this affect, as shown in FIG. 15, Japanese Patent Laid-Open No. 11-243132 (corresponding to U.S. Pat. No. 6,028,376) discloses a mechanism for canceling drive reaction-forces of the stage apparatus of an exposure apparatus. The exposure apparatus includes a base 109 supporting a stage 105 movable in the X- and Y-directions, respectively, with the aid of guides 107 and 121, a pair of mass bodies 113a and 113b and another pair of mass bodies 113c and 113d disposed thereto, respectively, driven in the X- and Y-axis directions. The base has a rotating mass body (not shown) disposed thereto, generating a rotating torque. With this structure, by driving the mass bodies so as to cancel the drive reaction-forces of the stage in the X- and Y-directions and the θ-direction (the rotating direction about the Z-axis), the affect of vibration caused by the drive reaction-forces is reduced.
Japanese Patent Laid-Open No. 11-190786 (corresponding to U.S. Pat. No. 6,414,742) discloses another mechanism shown in FIG. 16. A structure, in which the base 109 having the stage 105 placed thereon, is supported by an air bearing so as to be movable relative to a base 110. The base 109 has rotatable rotors 108 disposed on its side surfaces with this structure, the drive reaction-forces of the stage in the X- and Y-directions are cancelled by moving the base 109, and drive reaction-forces in the θ-direction, the ωx-direction (the rotating direction about the X-axis), and the-ωy direction (the rotating direction about the X-axis) are cancelled by rotating the rotors.
In recent years, the diameter of a wafer has been increasing for increasing productivity of devices. Accordingly, the stage has to have a larger diameter in proportion to an increase in the diameter of the wafer, and therefore a larger weight. Also, in order to increase throughput (the number of wafers processed in a unit time), it is necessary for the stage to move more quickly. To this end, the stage tends to be moved at a high acceleration. That is, the stage tends to be driven with a larger thrust force of than before due to its increased weight and higher acceleration.
With the structure of another mechanism disclosed in Japanese Patent Laid-Open No. 11-190786 in which reaction forces are canceled by moving the base 109 in the X- and Y-directions relative to the base 110, an additional space is needed by an amount equivalent to a stroke allowing the base 109 to move therealong. This causes the larger size of the overall stage apparatus and accordingly, the larger size of the exposure apparatus itself.
With this structure, the stroke of the base 109 could be reduced by making the base 109 heavier. However, in practice, the base 109 cannot be made too heavy when taking into account transportation, maintenance, and so forth of the stage apparatus.
Also, in the case where the base 109 is elevated by the air bearings, the air bearings are needed to have as large a capacity as to elevate the base 109 having a weight of several tons. Unfortunately, a larger capacity of the air bearings require a larger flow rate of feeding air, and this sometimes causes difficulty in installing the stage apparatus depending on its installation specifications.
The structure of another mechanism disclosed in Japanese Patent Laid-Open No. 11-243132, in which the base has mass bodies hung down from its side surfaces, results in an increased installation space. Also, the hanging structure of the mass bodies may cause an undesirable deformation and deterioration in posture of the base.